Power are indispensable major components provided in computers, electronic devices and communication equipments. The function is to provide one or more regulated voltage sources for the equipments.
The conventional regulated step-down switching circuit used for a power supply DC-to-DC converter is represented by the circuit shown within the solid line rectangular enclosure (A) in FIG. 1. Such a conventional switching circuit is available from the "Linear Technology Corporation". The circuit comprises two metal-oxide-semiconductor field effect transistors (MOS-FET11 and MOS-FET12), a transistor (Q11), a voltage regulator (IC1), two diodes (D12 and D14), two capacitors (C11 and C12) and resistors (R11, R12, R13, R14 and etc.). MOS-FET11 becomes conductive when the voltage applied at its gate is greater than the input voltage.
But this circuit possesses defects as follows: First, the circuit requires two MOSFET, a voltage regulator IC, a transistor, and a number of passive components such as capacitors, resistors, etc. because the circuitry of conventional converters is complex, more parts are required to construct such a circuit, and consequently, production costs are increased and reliability is reduced. Second, the voltage regulator IC of this circuit operated continuously so that it always consumes power.